This invention relates to a dynamic external fixator usable to aid in the treatment of bone fractures in the region of the human wrist. It is well known that closed cast immobilization is inadequate for the treatment of displaced fractures of the distal radius in which loss of length of the involved bones is a significant risk. This loss of length as well as loss of normal radial and volar tilt are directly correlated with insufficient and inferior treatment techniques. Loss of range of motion of the wrist joint due to inferior treatment techniques poses a serious problem.
As noted by Lidstrom in his article entitled "Fractures of the Distal End of the Radius: A Clinical and Statistical Study of End Results", concern with residual stiffness following closed methods of treatment is found in the works of multiple authors of the late 19th and 20th centuries. They advocated early range of motion without immobilization, thus recognizing the need for early motion, but failed to recognize the importance of maintenance of reduction. As further noted therein, long term studies with large numbers of patients have a shown a direct correlation of functional results to the adequacy and maintenance of reduction as well as to the severity of the original fracture. In the series reported by Lidstrom, fractures of the displaced, comminuted type treated by closed methods resulted in an 81% incidence of significant loss of motion. Therein, the results were also related to the types of fracture found and in situations where the fractures were of the displaced, comminuted type the results were either poor or fair in 56% of the cases.
It has also been recognized in the art that it is desirable for the wrist to have a certain degree of mobility during the treatment of wrist fractures. The prior art has advocated the use of a functional splint in order to maintain length and reduction while allowing motion, however, significant loss of volar tilt and collapse have been seen with both displaced extra-articular and intra-articular fractures.
The use of skeletal external fixation, generally speaking, is known and has been quite successful in maintaining length, volar and radial tilt and thus improving functional results in the healing of fractures. In the prior art, numerous modes are disclosed utilizing the combination of skeletal pin fixation and plaster. The use of the combination of plaster and skeletal pin fixation is not without its complications. D. P. Green in his paper "Comminuted Fractures of the Distal End of the Radius" notes that in a comprehensive series, 50% of the patients had loss of pronation-supination and only 15% of the patients had normal wrist motion at long term follow up. The most significant problem involved in the procedure involved pin care beneath the plaster and Green notes a 33% incidence of pin cite drainage problems.
The introduction of external skeletal fixation marked a significant advantage in the treatment of comminuted, displaced fractures of the distal radius. The principle employed in this procedure is that of longitudinal traction applied to the skeleton by proximal and distal pins. Maintenance of the device is necessary until healing is adequate to assure maintenance of reduction. Unfortunately, in the prior art, the system does not allow motion at the wrist during the period of fracture immobilization.
While the above described treatment is much improved over previous methods, significant problems result due to the prolonged immobilization of the wrist which is necessary during the treatment. W. P. Cooney, et al. in their paper "External Pin Fixation For Unstable Colles' Fractures" report on their review of 60 patients 2 years after a fracture of the wrist. Their review indicates that the range of motion of the wrist is decreased in most cases in all planes about the wrist. Thus while this method does maintain length and radial and volar tilt which are known to improve functional results, however, immobilization of the wrist during the healing process may result in prolonged recovery of motion or, as shown by Cooney, et al., residual loss of motion as late as two years post injury.
The following U.S. Patents are known to applicant: U.S. Pat. No. 1,789,060 to Weisenbach, U.S. Pat. No. 435,850 to Siebrandt U.S. Pat. No. 2,439,995 to Thrailkill, U.S. Pat. No. 3,941,123 to Volkov, et al. and U.S. Pat. No. 4,312,336 to Danieletto, et al. While these patents appear to be directed to external fixators of various types, the present invention is believed to be patentably distinct therefrom as teaching the combination of fixation of the wrist joint fracture while allowing freedom of movement of the joint itself, with the further provision of adjustability of the freedom of movement. These and other differences will become apparent from a reading of the specific description of the preferred embodiment hereinafter.